Cannot log in via desktop client with Login Flow v2

[savyajha]

Expected behaviour

Should be able to log in normally

Actual behaviour

Get this error: "There was an error accessing the 'token' endpoint: Error transferring https://domain/index.php/login/v2 - server replied: Internal Server Error"

Steps to reproduce

1. Download nextcloud desktop client on either Mac or Windows (Unconfirmed on Linux)
2. Try to log into account
3. Fail

Client configuration

Client version: 2.6.3 - 2.6.5. The bug is not present in 2.5.3 (I have downgraded and logged in just fine)

Operating system: Windows 10 as well as macOS Catalina

OS language: en-US (both)

Qt version used by client package (Linux only, see also Settings dialog): N/A

Client package (From Nextcloud or distro) (Linux only): N/A

Installation path of client: Standard paths for both Windows and Mac

Server configuration

Nextcloud version: 19.0.0

Storage backend (external storage): None (local disk)

Logs

Please use Gist (https://gist.github.com/) or a similar code paster for longer
logs.

1. Client logfile: Do not have this

2. Web server error log: No output related to this

3. Server logfile: (Taken from logging console in GUI):

Exception: Argument 1 passed to OC\Security\Crypto::encrypt() must be of the type string, null given, called in /var/lib/html/core/Service/LoginFlowV2Service.php on line 200
    /var/lib/html/lib/private/AppFramework/App.php - line 137:
    OC\AppFramework\Http\Dispatcher->dispatch(OC\Core\Cont ... {}, "init")
    /var/lib/html/lib/private/AppFramework/Routing/RouteActionHandler.php - line 47:
    OC\AppFramework\App::main("OC\\Core\\C ... r", "init", OC\AppFramew ... {}, { _route: "c ... "})
    <<closure>>
    OC\AppFramework\Routing\RouteActionHandler->__invoke({ _route: "c ... "})
    /var/lib/html/lib/private/Route/Router.php - line 297:
    call_user_func(OC\AppFramew ... {}, { _route: "c ... "})
    /var/lib/html/lib/base.php - line 1007:
    OC\Route\Router->match("/login/v2")
    /var/lib/html/index.php - line 37:
    OC::handleRequest()

Caused by TypeError: Argument 1 passed to OC\Security\Crypto::encrypt() must be of the type string, null given, called in /var/lib/html/core/Service/LoginFlowV2Service.php on line 200
    /var/lib/html/core/Service/LoginFlowV2Service.php - line 200:
    OC\Security\Crypto->encrypt("*** sensiti ... *")
    /var/lib/html/core/Controller/ClientFlowLoginV2Controller.php - line 229:
    OC\Core\Service\LoginFlowV2Service->createTokens("Mozilla/5.0 ... )")
    /var/lib/html/lib/private/AppFramework/Http/Dispatcher.php - line 170:
    OC\Core\Controller\ClientFlowLoginV2Controller->init()
    /var/lib/html/lib/private/AppFramework/Http/Dispatcher.php - line 100:
    OC\AppFramework\Http\Dispatcher->executeController(OC\Core\Cont ... {}, "init")
    /var/lib/html/lib/private/AppFramework/App.php - line 137:
    OC\AppFramework\Http\Dispatcher->dispatch(OC\Core\Cont ... {}, "init")
    /var/lib/html/lib/private/AppFramework/Routing/RouteActionHandler.php - line 47:
    OC\AppFramework\App::main("OC\\Core\\C ... r", "init", OC\AppFramew ... {}, { _route: "c ... "})
    <<closure>>
    OC\AppFramework\Routing\RouteActionHandler->__invoke({ _route: "c ... "})
    /var/lib/html/lib/private/Route/Router.php - line 297:
    call_user_func(OC\AppFramew ... {}, { _route: "c ... "})
    /var/lib/html/lib/base.php - line 1007:
    OC\Route\Router->match("/login/v2")
    /var/lib/html/index.php - line 37:
    OC::handleRequest()

[kesselb]

Looks like a server issue and similar to: nextcloud/server#16495

Index: core/Service/LoginFlowV2Service.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- core/Service/LoginFlowV2Service.php	(revision 7274186fa9322986791414d73675d52ea820e83c)
+++ core/Service/LoginFlowV2Service.php	(date 1594563079516)
@@ -225,7 +225,10 @@
 			throw new \RuntimeException('Could not initialize keys');
 		}
 
-		openssl_pkey_export($res, $privateKey);
+		if (openssl_pkey_export($res, $privateKey, null, $config) === false) {
+			$this->logOpensslError();
+			throw new \RuntimeException('OpenSSL reported a problem');
+		}
 
 		// Extract the public key from $res to $pubKey
 		$publicKey = openssl_pkey_get_details($res);

They above patch should either fix the issue (because the method is called the right way) or log a more meaningful error.

[savyajha]

Just tried this and it works. If it's not too much of an ask please do push this patch into the server, it seems fairly trivial. :)